Ready-to-eat breakfast cereals are popular food items which provide a good source of nutrition. Typical ready-to-eat breakfast cereals are prepared in a variety of ways to provide different textures and mouthfeel. Such breakfast cereals include flaked cereals, puffed cereals, and shredded cereals.
Ready-to-eat cereals are formulated primarily with cereal grains, and may contain one or more cereal grains. The cereal grains utilized, such as corn, wheat, rice, barley, and the like, have a high starch content but relatively little protein. A cereal having more protein content, therefore, is desirable from a nutritional standpoint.
Soybeans are an excellent source of protein, and it has been recognized in the past, for example in U.S. Pat. No. 2,421,216, that combining soy protein and other high starch cereal grains in a ready-to-eat breakfast cereal would provide a breakfast cereal with an improved nutritional profile. Soy protein has a desirable amino acid profile for nutritional purposes, and includes other health promoting elements such as phytoestrogens. Soy protein has also recently been shown to lower blood cholesterol concentrations in hypercholesterolemic individuals. A breakfast cereal containing soy protein, therefore, is very desirable since the cereal would provide an excellent source of protein, a good nutritional amino acid profile, and could be used to lower blood cholesterol concentration in hypercholesterolemic consumers.
Unfortunately, soy protein has not been widely used in ready-to-eat breakfast cereals for several reasons. First, inexpensive but relatively unprocessed comminuted whole soybeans and soy flours, grits, and flakes contain high levels of oligosaccharides, especially raffinose and stachyose, which induce intestinal gas and corresponding discomfort and flatus. Humans lack the .alpha.-galactosidase enzyme needed to break down and digest complex oligosaccharides such as raffinose and stachyose into simple carbohydrates such as glucose, fructose, and sucrose which can be easily absorbed by the gut. Instead of being absorbed by the gut, soy raffinose and stachyose enter the lower intestine where they are fermented by bacteria to cause intestinal gas and flatus. The demand for comminuted whole soybeans and soy flours, grits, and flakes in cereals, therefore, has been understandably muted.
Second, the relatively unprocessed comminuted whole soybeans and soy flours, grits, and flakes have a beany and bitter taste which diminishes the palatability of a cereal incorporating these materials. The poor palatability of the comminuted whole soybeans and soy flours, grits, and flakes, combined with their poor digestability, has made such soy materials unattractive for incorporation into cereals.
Third, soy materials which have been processed to remove oligosaccharides and poor taste factors (e.g. soy protein concentrates and soy protein isolates) are substantially more expensive ingredients than comminuted whole soybeans or soy flours, grits, and flakes. Soy protein concentrates and soy protein isolates are formed from soy flour, grits, or flakes which are processed to remove water soluble and/or alcohol soluble components, including raffinose and stachyose. Soy protein concentrates are formed by:
i) washing a soy flour/flake/grit material with an aqueous alcohol; ii) leaching a soy flour/flake/grit material with an aqueous acid having a pH around the isoelectric point of soy protein (pH 4.5); or extracting a soy flake/flour/grit material with a moist heat (e.g. steam). Soy protein isolates are formed from a soy flake/flour/grit material by extracting the protein with an aqueous alkali extract, separating the protein containing extract from insoluble fiber materials, precipitating the protein from the extract by adjusting the pH of the extract to about the isoelectric point of the protein; and separating the precipitated protein from the extract. On a commercial scale, processes to refine soy protein products into soy protein concentrates and soy protein isolates are quite expensive, and the expense of the resultant processed soy materials has made them unattractive as cereal ingredients.
It is desirable, therefore, to obtain a cereal composition containing soy protein which utilizes relatively unprocessed soy protein containing ingredients but which contains little or no raffinose or stachyose and which has a pleasant taste. It is also desirable to provide a process for obtaining such a cereal composition.